Fuel retention measurement on plasma-facing components is an active field of study in magnetic confinement nuclear fusion devices.The laser-induced breakdown spectroscopy(LIBS)diagnostic method has been well demonstra...Fuel retention measurement on plasma-facing components is an active field of study in magnetic confinement nuclear fusion devices.The laser-induced breakdown spectroscopy(LIBS)diagnostic method has been well demonstrated to detect the elemental distribution in PFCs.In this work,an upgraded co-axis LIBS system based on a linear fiber bundle collection system has been developed to measure the hydrogen(H) retention on a tantalum(Ta) sample under a vacuum condition.The spatial resolution measurement of the different positions of the LIBS plasma can be achieved simultaneously with varying delay times.The temporal and spatial evolution results of LIBS plasma emission show that the H plasma observably expands from the delay times of 0-200 ns.The diameter of Ta plasma is about 6 mm which is much less than the size of H plasma after 200 ns.The difference in the temporal and spatial evolution behaviors between H plasma and Ta plasma is due to the great difference in the atomic mass of H and Ta.The depth profile result shows that H retention mainly exists on the surface of the sample.The temporal and spatial evolution behaviors of the electron excited temperature are consistent with that of the Ta emission.The result will further improve the understanding of the evolution of the dynamics of LIBS plasma and optimize the current collection system of in situ LIBS in fusion devices.展开更多
The population spatial distribution pattern and its evolving pattern play an important role in regional allocation of social resources and production factors, formulation of regional development plans, construction of...The population spatial distribution pattern and its evolving pattern play an important role in regional allocation of social resources and production factors, formulation of regional development plans, construction of a better life society, and promotion of regional economic development. Based on the resident population statistics data of Henan province from 2006 to 2021, with county as the basic study unit, the paper studies the spatial morphology characteristics and its evolution patterns of resident population distribution, by using spatial analysis methods such as population distribution center, standard deviation ellipse, and spatial auto correlation analysis. The results show that: the resident population spatial distribution shows unbalanced state, the population agglomeration areas mainly distribute in the northeast part and north part, where the resident population growth rate is significantly higher than other regions, over time, this trend is gradually becoming significant. The resident population distribution has a trend of centripetal concentration, with the degree and trend of centripetal gradually strengthening. The resident population distribution has obvious directional characteristics, but the significance is not high, the weighted resident population average center is approximately located at (4.13740˚N, 113.8935˚E), and the azimuth of the distribution axis is approximately 11.19˚. The population distribution has obvious agglomeration characteristics, with the built-up areas of Zhengzhou and Luoyang as their centers, where have a significant siphon effect on the surrounding population. The southern and southwestern regions in the province form a relatively stable belt area of Low-Low agglomeration areas.展开更多
Tungsten(W)is an important material in tokamak walls and divertors.The W ion charge state distribution and the dynamic behavior of ions play important roles in the investigation of plasma–wall interactions using lase...Tungsten(W)is an important material in tokamak walls and divertors.The W ion charge state distribution and the dynamic behavior of ions play important roles in the investigation of plasma–wall interactions using laser-ablation-based diagnostics such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy.In this work,we investigate the temporal and spatial evolutions of differently charged ions in a nanosecond-laser-produced W plasma in vacuum using time-of-flight mass spectroscopy.Ions with different charge states from 1 to 7(W+to W7+)are all observed.The temporal evolutions of the differently charged ions show that ions with higher charge states have higher velocities,indicating that space separation occurs between the differently charged ion groups.Spatially-resolved mass spectroscopy measurements further demonstrate the separation phenomenon.The temporal profile can be accurately fitted by a shifted Maxwell–Boltzmann distribution,and the velocities of the differently charged ions are also obtained from the fittings.It is found that the ion velocities increase continuously from the measured position of 0.75 cm to 2.25 cm away from the target surface,which indicates that the acceleration process lasts through the period of plasma expansion.The acceleration and space separation of the differently charged ions confirm that there is a dynamic plasma sheath in the laser-produced plasma,which provides essential information for the theoretical laser-ablation model with plasma formation and expansion.展开更多
Suaeda salsa is an important local species in the intertidal beach of the Western Pacific coast. However,under the artificial cofferdam and Spartina alterniflora expansion,Suaeda marsh has degraded seriously. Therefor...Suaeda salsa is an important local species in the intertidal beach of the Western Pacific coast. However,under the artificial cofferdam and Spartina alterniflora expansion,Suaeda marsh has degraded seriously. Therefore,using Yancheng Nature Reserve as a case study area,taking ETM+images in 2000,2006 and 2011 as the basic data sources,we revealed the evolution characteristics of Salsa marsh which was impacted. The research results are as follows. From 2000 to 2011,Salsa marsh area in the artificial area tempestuously degraded,decreasing by 87. 158%,more than 22% than those in the natural area. The landscape was fragmentized. Landscape polymerization degree index dropped from 95. 780 to 65. 455,more than 16% than those in the natural area. The mean patch area fell down to 21. 429 ha from 389. 333 ha,more than 11% that in the natural area. Compared to the steady change in natural conditions,the area was reduced by 118. 167 ha/a from 2000 to 2006,while during 2006-2011,it was only 51. 500 ha/a in artificial area. As for spatial change of landscape,in artificial area,the Salsa marsh centroid moved forward to the southeast with 666. 350 m,but that in natural area moved forward to the north with 1 042. 710 m from 2000 to 2006. From 2006 to 2011,the centroid moved forward to east and north respectively. Artificial cofferdam transformed the area into freshwater ecosystem,and meanwhile the freshwater was beneficial to Reed marsh. During 2000 to 2006,in the artificial area,539 ha Salsa marsh controlled by cofferdam transferred into reed marsh and aquaculture ponds,of which the transformation rate was nearly 4% higher than that in natural area. From 2006 to 2011,178 ha Salsa marsh was transferred into reed marsh,the transformation rate was 20% higher than that in natural area. With rapid spreading and strong competition of Spartina species,the coastal wetland has formed the pattern of " Salsa – Spartina marshes". From 2000 to 2006,in artificial area,15. 24% of Salsa marsh was transferred into Spartina marsh,of which the transformation rate was13% higher than that in natural area. And from 2006 to 2011,30. 07% Salsa marsh was replaced by the Spartina marsh in artificial area,the rate was almost 10% higher than that in the natural area.展开更多
With the rapid development of China's economy,people's demand for a healthy living environment is increasing,and air quality has gradually been widely concerned by all sectors of society.Using the big data of ...With the rapid development of China's economy,people's demand for a healthy living environment is increasing,and air quality has gradually been widely concerned by all sectors of society.Using the big data of air quality monitoring from 1998 to 2016,based on the exploratory spatio-temporal analysis method,this paper explored the spatio-temporal evolution of PM_(2.5) at the national scale,and drew the following conclusions:①PM_(2.5) heavy pollution is mainly in central and eastern China,north and south China,and the pollution degree is relatively light in northwest and northeast China.Meanwhile,PM_(2.5) concentration in heavily polluted areas increased significantly over time,while PM_(2.5) concentration in low-polluted areas showed a long-term stable trend.②The number and area of cities with moderate and high PM_(2.5) pollution levels showed an inverted U-shaped curve from 1998 to 2016,and 2007 was the inflection point.③The spatial autocorrelation coefficient of PM_(2.5) is high over the years,and the spatial neighbor effect of PM_(2.5) is significant.The high-pollution clusters are mainly concentrated in the Beijing-Tianjin-Hebei region,the Yangtze River Delta and the Pearl River Delta,and the pollution concentration in these three regions has increased rapidly in recent years.It is necessary to focus on joint prevention and control.展开更多
To study the temporal and spatial changes of heat resources to serve agricultural production and economic development. The climate data from 1958 to 2017 were selected, and the temporal and spatial changes of heat res...To study the temporal and spatial changes of heat resources to serve agricultural production and economic development. The climate data from 1958 to 2017 were selected, and the temporal and spatial changes of heat resources in Liaoning, China were analyzed by using the method of climate diagnosis and analysis. The results show that: the southern coastal area of Liaoning has the most heat resources, the northwestern hilly area and the eastern mountainous area the least, and the central plain area in the middle distribution pattern;compared with 1958-1980, 1981-2017 ≥0°C, ≥10°C accumulated temperature, etc. The value line is advanced 100-160km northward. The accumulated temperature of ≥0°C and ≥10°C in Liaoning experienced abrupt changes in climate in 1993 and 1994, and the climate abrupt change in the southern coastal area was earlier than that in the inland. , the increase in the northwestern hilly area and the eastern mountainous area is less than that in the central plain area and the southern coastal area. The study on the impact on meteorological services found that the increase or decrease of heat resources has a significant impact on agro-meteorological services, which can prolong the growing season of crops, relatively reduce the damage of frost, improve comprehensive utilization of land, and increase crop yields;at the same time, with the increase of heat resources and the northward expansion of the isoline of accumulated temperature, the area affected by pests and diseases has expanded, which has aggravated the harm to agriculture economic burden.展开更多
基金supported by National Key R&D Program of China(No.2017TFE0301300)the National Natural Science Foundation of China(Nos.11605023,11805028,11861131010)the China Postdoctoral Science Foundation(Nos.2017T100172,2016M591423)。
文摘Fuel retention measurement on plasma-facing components is an active field of study in magnetic confinement nuclear fusion devices.The laser-induced breakdown spectroscopy(LIBS)diagnostic method has been well demonstrated to detect the elemental distribution in PFCs.In this work,an upgraded co-axis LIBS system based on a linear fiber bundle collection system has been developed to measure the hydrogen(H) retention on a tantalum(Ta) sample under a vacuum condition.The spatial resolution measurement of the different positions of the LIBS plasma can be achieved simultaneously with varying delay times.The temporal and spatial evolution results of LIBS plasma emission show that the H plasma observably expands from the delay times of 0-200 ns.The diameter of Ta plasma is about 6 mm which is much less than the size of H plasma after 200 ns.The difference in the temporal and spatial evolution behaviors between H plasma and Ta plasma is due to the great difference in the atomic mass of H and Ta.The depth profile result shows that H retention mainly exists on the surface of the sample.The temporal and spatial evolution behaviors of the electron excited temperature are consistent with that of the Ta emission.The result will further improve the understanding of the evolution of the dynamics of LIBS plasma and optimize the current collection system of in situ LIBS in fusion devices.
文摘The population spatial distribution pattern and its evolving pattern play an important role in regional allocation of social resources and production factors, formulation of regional development plans, construction of a better life society, and promotion of regional economic development. Based on the resident population statistics data of Henan province from 2006 to 2021, with county as the basic study unit, the paper studies the spatial morphology characteristics and its evolution patterns of resident population distribution, by using spatial analysis methods such as population distribution center, standard deviation ellipse, and spatial auto correlation analysis. The results show that: the resident population spatial distribution shows unbalanced state, the population agglomeration areas mainly distribute in the northeast part and north part, where the resident population growth rate is significantly higher than other regions, over time, this trend is gradually becoming significant. The resident population distribution has a trend of centripetal concentration, with the degree and trend of centripetal gradually strengthening. The resident population distribution has obvious directional characteristics, but the significance is not high, the weighted resident population average center is approximately located at (4.13740˚N, 113.8935˚E), and the azimuth of the distribution axis is approximately 11.19˚. The population distribution has obvious agglomeration characteristics, with the built-up areas of Zhengzhou and Luoyang as their centers, where have a significant siphon effect on the surrounding population. The southern and southwestern regions in the province form a relatively stable belt area of Low-Low agglomeration areas.
基金supported by the National Key R&D Program of China(No.2017YFE0301304)National Natural Science Foundation of China(No.12005034)the China Postdoctoral Science Foundation(No.2019M661087)supported by the US Department of Energy,Office of Defense Nuclear Nonproliferation Research and Development,under contract number DE-AC02-05CH11231 at the Lawrence Berkeley National Laboratory。
文摘Tungsten(W)is an important material in tokamak walls and divertors.The W ion charge state distribution and the dynamic behavior of ions play important roles in the investigation of plasma–wall interactions using laser-ablation-based diagnostics such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy.In this work,we investigate the temporal and spatial evolutions of differently charged ions in a nanosecond-laser-produced W plasma in vacuum using time-of-flight mass spectroscopy.Ions with different charge states from 1 to 7(W+to W7+)are all observed.The temporal evolutions of the differently charged ions show that ions with higher charge states have higher velocities,indicating that space separation occurs between the differently charged ion groups.Spatially-resolved mass spectroscopy measurements further demonstrate the separation phenomenon.The temporal profile can be accurately fitted by a shifted Maxwell–Boltzmann distribution,and the velocities of the differently charged ions are also obtained from the fittings.It is found that the ion velocities increase continuously from the measured position of 0.75 cm to 2.25 cm away from the target surface,which indicates that the acceleration process lasts through the period of plasma expansion.The acceleration and space separation of the differently charged ions confirm that there is a dynamic plasma sheath in the laser-produced plasma,which provides essential information for the theoretical laser-ablation model with plasma formation and expansion.
基金Supported by National Natural Science Foundation of China(41771199)Basic Research Project of Jiangsu Province,China(BK20171277)
文摘Suaeda salsa is an important local species in the intertidal beach of the Western Pacific coast. However,under the artificial cofferdam and Spartina alterniflora expansion,Suaeda marsh has degraded seriously. Therefore,using Yancheng Nature Reserve as a case study area,taking ETM+images in 2000,2006 and 2011 as the basic data sources,we revealed the evolution characteristics of Salsa marsh which was impacted. The research results are as follows. From 2000 to 2011,Salsa marsh area in the artificial area tempestuously degraded,decreasing by 87. 158%,more than 22% than those in the natural area. The landscape was fragmentized. Landscape polymerization degree index dropped from 95. 780 to 65. 455,more than 16% than those in the natural area. The mean patch area fell down to 21. 429 ha from 389. 333 ha,more than 11% that in the natural area. Compared to the steady change in natural conditions,the area was reduced by 118. 167 ha/a from 2000 to 2006,while during 2006-2011,it was only 51. 500 ha/a in artificial area. As for spatial change of landscape,in artificial area,the Salsa marsh centroid moved forward to the southeast with 666. 350 m,but that in natural area moved forward to the north with 1 042. 710 m from 2000 to 2006. From 2006 to 2011,the centroid moved forward to east and north respectively. Artificial cofferdam transformed the area into freshwater ecosystem,and meanwhile the freshwater was beneficial to Reed marsh. During 2000 to 2006,in the artificial area,539 ha Salsa marsh controlled by cofferdam transferred into reed marsh and aquaculture ponds,of which the transformation rate was nearly 4% higher than that in natural area. From 2006 to 2011,178 ha Salsa marsh was transferred into reed marsh,the transformation rate was 20% higher than that in natural area. With rapid spreading and strong competition of Spartina species,the coastal wetland has formed the pattern of " Salsa – Spartina marshes". From 2000 to 2006,in artificial area,15. 24% of Salsa marsh was transferred into Spartina marsh,of which the transformation rate was13% higher than that in natural area. And from 2006 to 2011,30. 07% Salsa marsh was replaced by the Spartina marsh in artificial area,the rate was almost 10% higher than that in the natural area.
基金Supported by the National Natural Science Foundation of China(51808413)General Project of Hubei Social Science Fund(Later Funded Project)(2020158)Innovation and Entrepreneurship Training Program for College Students in Hubei Province(S202010490027)。
文摘With the rapid development of China's economy,people's demand for a healthy living environment is increasing,and air quality has gradually been widely concerned by all sectors of society.Using the big data of air quality monitoring from 1998 to 2016,based on the exploratory spatio-temporal analysis method,this paper explored the spatio-temporal evolution of PM_(2.5) at the national scale,and drew the following conclusions:①PM_(2.5) heavy pollution is mainly in central and eastern China,north and south China,and the pollution degree is relatively light in northwest and northeast China.Meanwhile,PM_(2.5) concentration in heavily polluted areas increased significantly over time,while PM_(2.5) concentration in low-polluted areas showed a long-term stable trend.②The number and area of cities with moderate and high PM_(2.5) pollution levels showed an inverted U-shaped curve from 1998 to 2016,and 2007 was the inflection point.③The spatial autocorrelation coefficient of PM_(2.5) is high over the years,and the spatial neighbor effect of PM_(2.5) is significant.The high-pollution clusters are mainly concentrated in the Beijing-Tianjin-Hebei region,the Yangtze River Delta and the Pearl River Delta,and the pollution concentration in these three regions has increased rapidly in recent years.It is necessary to focus on joint prevention and control.
文摘To study the temporal and spatial changes of heat resources to serve agricultural production and economic development. The climate data from 1958 to 2017 were selected, and the temporal and spatial changes of heat resources in Liaoning, China were analyzed by using the method of climate diagnosis and analysis. The results show that: the southern coastal area of Liaoning has the most heat resources, the northwestern hilly area and the eastern mountainous area the least, and the central plain area in the middle distribution pattern;compared with 1958-1980, 1981-2017 ≥0°C, ≥10°C accumulated temperature, etc. The value line is advanced 100-160km northward. The accumulated temperature of ≥0°C and ≥10°C in Liaoning experienced abrupt changes in climate in 1993 and 1994, and the climate abrupt change in the southern coastal area was earlier than that in the inland. , the increase in the northwestern hilly area and the eastern mountainous area is less than that in the central plain area and the southern coastal area. The study on the impact on meteorological services found that the increase or decrease of heat resources has a significant impact on agro-meteorological services, which can prolong the growing season of crops, relatively reduce the damage of frost, improve comprehensive utilization of land, and increase crop yields;at the same time, with the increase of heat resources and the northward expansion of the isoline of accumulated temperature, the area affected by pests and diseases has expanded, which has aggravated the harm to agriculture economic burden.
